/*
 * Copyright 2010 Mario Zechner (contact@badlogicgames.com), Nathan Sweet (admin@esotericsoftware.com)
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS"
 * BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package com.badlogic.gdx.math.collision;

import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Vector3;

/**
 * Encapsulates a ray having a starting position and a unit length direction.
 * 
 * @author badlogicgames@gmail.com
 * 
 */
public final class Ray {
	public final Vector3 origin = new Vector3();
	public final Vector3 direction = new Vector3();

	/**
	 * Constructor, sets the starting position of the ray and the direction.
	 * 
	 * @param origin The starting position
	 * @param direction The direction
	 */
	public Ray (Vector3 origin, Vector3 direction) {
		this.origin.set(origin);
		this.direction.set(direction).nor();
	}

	/**
	 * @return a copy of this ray.
	 */
	public Ray cpy () {
		return new Ray(this.origin, this.direction);
	}

	/**
	 * Returns and endpoint given the distance. This is calculated as startpoint + distance * direction.
	 * 
	 * @param distance The distance from the end point to the start point.
	 * @return The end point
	 */
	public Vector3 getEndPoint (float distance) {
		return new Vector3(origin).add(direction.tmp().mul(distance));
	}

	static Vector3 tmp = new Vector3();

	/**
	 * Multiplies the ray by the given matrix. Use this to transform a ray into another coordinate system.
	 * 
	 * @param matrix The matrix
	 * @return This ray for chaining.
	 */
	public Ray mul (Matrix4 matrix) {
		tmp.set(origin).add(direction);
		tmp.mul(matrix);
		origin.mul(matrix);
		direction.set(tmp.sub(origin));
		return this;
	}

	/**
	 * {@inheritDoc}
	 */
	public String toString () {
		return "ray [" + origin + ":" + direction + "]";
	}

	/**
	 * Sets the starting position and the direction of this ray.
	 * 
	 * @param origin The starting position
	 * @param direction The direction
	 * @return this ray for chaining
	 */
	public Ray set (Vector3 origin, Vector3 direction) {
		this.origin.set(origin);
		this.direction.set(direction);
		return this;
	}

	/**
	 * Sets this ray from the given starting position and direction.
	 * 
	 * @param x The x-component of the starting position
	 * @param y The y-component of the starting position
	 * @param z The z-component of the starting position
	 * @param dx The x-component of the direction
	 * @param dy The y-component of the direction
	 * @param dz The z-component of the direction
	 * @return this ray for chaining
	 */
	public Ray set (float x, float y, float z, float dx, float dy, float dz) {
		this.origin.set(x, y, z);
		this.direction.set(dx, dy, dz);
		return this;
	}

	/**
	 * Sets the starting position and direction from the given ray
	 * 
	 * @param ray The ray
	 * @return This ray for chaining
	 */
	public Ray set (Ray ray) {

		this.origin.set(ray.origin);
		this.direction.set(ray.direction);
		return this;
	}
}
